Pin electronics (PE) circuitry that is incorporated within Automated Test Equipment (ATE) often needs to be protected from electrostatic discharge (ESD). Traditionally, PE circuitry, when inactive, has been protected from external overstress with mechanical relays. More recent ATE systems have been implemented with solid state relays or switches in order to save space, cost, power and to improve reliability. The use of solid state relays in an ATE architecture necessarily leaves the solid state relay physically connected to the external environment even when disabled. The relays will be open in the disabled state. By being open during user events, the relays protect the PE circuitry. However, to be open, the solid state relays must be powered up and still connected to the DUT node itself, thereby making the solid state relays themselves subject and vulnerable to ESD events. During this disabled state overstress ESD events can occur.
Not all ATE architectures without mechanical relays necessarily use solid state relays. With or without the use of solid state relays, it is possible for the PE circuitry to be physically connected to the external environment. Furthermore, users of ATE may not power down the ATE PE circuitry during typical disable modes, such as swapping out wafers/DUT's, because the overhead associated with powering back up, loading software, calibrating the system and waiting for temperature to stabilize, may be significant. Consequently, the ATE PE circuitry and the solid state relays may always be powered up during these disable modes. Thus, there is a need for enhanced overstress protection when in the disabled state and when the ATE may be drawing power.